next up previous
Next: About this document ... Up: A Non-Photorealistic Lighting Model Previous: Acknowledgments

Figure 3: Diffuse shaded image using Equation 1 with kd = 1 and ka = 0. Black shaded regions hide details, especially in the small claws; edge lines could not be seen if added. Highlights and fine details are lost in the white shaded regions.

Figure 4: Image with only highlights and edges. The edge lines provide divisions between object pieces and the highlights convey the direction of the light. Some shape information is lost, especially in the regions of high curvature of the object pieces. However, these highlights and edges could not be added to Figure 3 because the highlights would be invisible in the light regions and the silhouettes would be invisible in the dark regions.

Figure 5: Phong shaded image with edge lines and kd = 0.5 and ka = 0.1. Like Figure 3, details are lost in the dark grey regions, especially in the small claws, where they are colored the constant shade of kd ka regardless of surface orientation. However, edge lines and highlights provide shape information that was gained in Figure 4, but couldn't be added to Figure 3.

Figure 6: Approximately constant luminance tone rendering. Edge lines and highlights are clearly noticeable. Unlike Figures 3 and 5 some details in shaded regions, like the small claws, are visible. The lack of luminance shift makes these changes subtle.

Figure 7: Luminance/hue tone rendering. This image combines the luminance shift of Figure 3 and the hue shift of Figure 6. Edge lines, highlights, fine details in the dark shaded regions such as the small claws, as well as details in the high luminance regions are all visible. In addition, shape details are apparent unlike Figure 4 where the object appears flat. In this figure, the variables of Equation 2 and Equation 3 are: b = 0.4, y = 0.4, $\alpha$ = 0.2, and $\beta$ = 0.6.

Figure 8: Luminance/hue tone rendering, similar to Figure 7 except b = 0.55, y = 0.3, $\alpha$ = 0.25, and $\beta$ = 0.5. The different values of b and y determine the strength of the overall temperature shift, where as $\alpha$ and $\beta$ determine the prominence of the object color, and the strength of the luminance shift.

Figure 9: Top: Colored Phong-shaded spheres with edge lines and highlights. Bottom: Colored spheres shaded with hue and luminance shift, including edge lines and highlights. Note: In the first Phong shaded sphere (violet), the edge lines disappear, but are visible in the corresponding hue and luminance shaded violet sphere. In the last Phong shaded sphere (white), the highlight vanishes, but is noticed in the corresponding hue and luminance shaded white sphere below it. The spheres in the second row also retain their ``color name''.

Figure 10: Left to Right: a) Phong shaded object. b) New metal-shaded object without edge lines. c) New metal-shaded object with edge lines. d) New metal-shaded object with a cool-to-warm shift.

Figure 11: Left to Right: a) Phong model for colored object. b) New shading model with highlights, cool-to-warm hue shift, and without edge lines. c) New model using edge lines, highlights, and cool-to-warm hue shift. d) Approximation using conventional Phong shading, two colored lights, and edge lines.


Irving Biederman and Ginny Ju.
Surface versus Edge-Based Determinants of Visual Recognition.
Cognitive Psychology, 20:38-64, 1988.

Faber Birren.
Color Perception in Art.
Van Nostrand Reinhold Company, 1976.

Wendy L. Braje, Bosco S. Tjan, and Gordon E. Legge.
Human Efficiency for Recognizing and Detecting Low-pass Filtered Objects.
Vision Research, 35(21):2955-2966, 1995.

Tom Browning.
Timeless Techniques for Better Oil Paintings.
North Light Books, 1994.

Chris Christou, Jan J. Koenderink, and Andrea J. van Doorn.
Surface Gradients, Contours and the Perception of Surface Attitude in Images of Complex Scenes.
Perception, 25:701-713, 1996.

Cassidy J. Curtis, Sean E. Anderson, Kurt W. Fleischer, and David H. Salesin.
Computer-Generated Watercolor.
In SIGGRAPH 97 Conference Proceedings, August 1997.

Debra Dooley and Michael F. Cohen.
Automatic Illustration of 3D Geometric Models: Surfaces.
IEEE Computer Graphics and Applications, 13(2):307-314, 1990.

Gershon Elber and Elaine Cohen.
Hidden Curve Removal for Free-Form Surfaces.
In SIGGRAPH 90 Conference Proceedings, August 1990.

E. Bruce Goldstein.
Sensation and Perception.
Wadsworth Publishing Co., Belmont, California, 1980.

Paul Haeberli.
Paint By Numbers: Abstract Image Representation.
In SIGGRAPH 90 Conference Proceedings, August 1990.

Paul Haeberli.
The Accumulation Buffer: Hardware Support for High-Quality Rendering.
SIGGRAPH 90 Conference Proceedings, 24(3), August 1990.

Patricia Lambert.
Controlling Color: A Practical Introduction for Designers and Artists, volume 1.
Everbest Printing Company Ltd., 1991.

Peter Litwinowicz.
Processing Images and Video for an Impressionistic Effect.
In SIGGRAPH 97 Conference Proceedings, August 1997.

L. Markosian, M. Kowalski, S. Trychin, and J. Hughes.
Real-Time Non-Photorealistic Rendering.
In SIGGRAPH 97 Conference Proceedings, August 1997.

Judy Martin.
Technical Illustration: Materials, Methods, and Techniques, volume 1.
Macdonald and Co Publishers, 1989.

Barbara J. Meier.
Painterly Rendering for Animation.
In SIGGRAPH 96 Conference Proceedings, August 1996.

Bui-Tuong Phong.
Illumination for Computer Generated Images.
Communications of the ACM, 18(6):311-317, June 1975.

Tom Ruppel, editor.
The Way Science Works, volume 1.
MacMillan, 1995.

Takafumi Saito and Tokiichiro Takahashi.
Comprehensible Rendering of 3D Shapes.
In SIGGRAPH 90 Conference Proceedings, August 1990.

Mike Salisbury, Michael T. Wong, John F. Hughes, and David H. Salesin.
Orientable Textures for Image-Based Pen-and-Ink Illustration.
In SIGGRAPH 97 Conference Proceedings, August 1997.

Doree Duncan Seligmann and Steven Feiner.
Automated Generation of Intent-Based 3D Illustrations.
In SIGGRAPH 91 Conference Proceedings, July 1991.

Bosco S. Tjan, Wendy L. Braje, Gordon E. Legge, and Daniel Kersten.
Human Efficiency for Recognizing 3-D Objects in Luminance Noise.
Vision Research, 35(21):3053-3069, 1995.

Edward Tufte.
Visual Explanations.
Graphics Press, 1997.

Bruce Walter, Gun Alppay, Eric P. F. Lafortune, Sebastian Fernandez, and Donald P. Greenberg.
Fitting Virtual Lights for Non-Diffuse Walkthroughs.
In SIGGRAPH 97 Conference Proceedings, pages 45-48, August 1997.

Lance Williams.
Shading in Two Dimensions.
Graphics Interface '91, pages 143-151, 1991.

Georges Winkenbach and David H. Salesin.
Computer Generated Pen-and-Ink Illustration.
In SIGGRAPH 94 Conference Proceedings, August 1994.

next up previous Next: About this document ... Up: A Non-Photorealistic Lighting Model Previous: Acknowledgments
Bruce or Amy Gooch